1. Field of the Invention
The present invention relates generally to the fields of cell biology, cancer biology, and immunology. More particularly, it concerns cells that have been engineered by loading them with chemical and biological agents and the resultant entities used as therapeutics in the treatment of multiple indications, including cancer.
2. Description of Related Art
Mononuclear cells, encompassing for example hematopoietic stem cells, mesenchymal stem cells, endothelial progenitor cells, adipose derived stem cells, and peripheral blood mononuclear cells (PBMC), have been used in multiple applications for treatment of immune diseases and in regenerative medicine applications (Passweg J and Tyndall A., Semin Hematol. 2007 October 44(4):278-85; Le Blanc K and Ringdén O. Intern Med. 2007 November 262(5):509-25; Ward et al. Catheter Cardiovasc Interv. 2007 Dec. 1 70(7):983-98; Mimeault et al., Clin Pharmacol Ther. September 2007 82(3):252-64 Epub 2007 Aug. 1).
Peripheral blood mononuclear cells (PBMC) are comprised of cells of myeloid and lymphoid lineages. Myeloid cells, such as monocytes, macrophages, dendritic cells (DC), when loaded with antigens have been demonstrated to be effective antigen presenting cells for generation of tumor-antigen specific immune responses for treatment of cancer or for modulation of self-antigen specific T cells and regulatory T cells in control of autoimmunity (Gilboa E., J Clin Invest. 2007 May 117(5):1195-203). Lymphoid cells, such as T cells, NK cells, B cells, lymphoid DC, are effective mediators of immune responses and can be further harnessed to also present antigen and stimulate naive and memory responses (Hong C and Park S H. Crit Rev Immunol. 2007 27(6):511-25; Martino A and Poccia F, Curr Mol Med. 2007 November 7(7):658-73).
Antigen Presenting Cells (APC) are important sentinels for detecting and presenting antigens to the immune effector cells. They have been extensively studied for becoming the effective therapeutic agents. Factors of antigen-loading, process and presentation in the context of state of maturity of APC to engage effector cells are major concerns in the design and development of APC-based immunotherapies and vaccines. Electroloading of tumor antigens, provided in the form of nucleotides (DNA, mRNA) or proteins/lysates or multimeric antigenic formulations, allows for effective uptake and processing of antigens in freshly isolated cells without requiring efficient maturation of APC antigen uptake mechanisms. Further other chemical and/or biological agents can be electro-loaded into APC to affect antigen-processing, processed antigen presentation, or immuno-regulatory environment in subject/patient such that the effective biological activity of electro-loaded APC is engineered to be superior to that of naive freshly isolated APC. Such antigen-loading or antigen-loading combined with enhancement of biological activity for freshly isolated (naïve) APC is a unique attribute of the composition of PBMC thus loaded allowing for rapid formulation and delivery of product to subject/patient. Such biological activity otherwise would only be imparted following processes that require elaborate cell culture, expansion, differentiation, maturation of other manipulation processes that do not lend themselves to delivery of a therapeutic composition of APC immunotherapy and vaccine products in clinically relevant timeframe for administration to subject/patient in a hospital/physician's office setting.
NK and T cells are important mediators of viral and tumor immune responses. They have been extensively studied for becoming the efficient therapeutic agents. Factors of efficient and specific target cell killing, procedure simplicity, cell availability and low graft versus host disease (GvHD) are the major concerns. Chimeric receptor constructs have been described which, when expressed in cells of the immune system, can enhance the immunological specific response to tumor cells and thereby bring clinical benefit to cancer patients. Expanded NK and T cells expressing a chimeric receptor can overcome HLA-type-related inhibition of the expanded NK cell killing and T cell receptor (TCR)-required T cell killing of targeted tumor cells (Imai et al. 2004). However, considering the simplicity of using resting NK or T cells, if the resting NK or T cells, either autologous or allogeneic, could be engineered to have both efficient and specific target cell killing, it will be the desired for the tumor therapy. Furthermore, if resting peripheral blood lymphocytes (PBL) or even peripheral blood mononuclear cells (PBMC) could be engineered to have both efficient and specific target cell killing, it will be the most desired for the tumor therapy because of procedural simplicity and cell availability. Regular retroviral vectors could not infect resting NK or T cells. Lentiviral vectors have been used to transfect resting peripheral blood lymphocytes (Simmons et al. 2006). Unfortunately, use of viral vectors entails safety and practical problems for clinical application.
Electroporation is a well recognized method for loading nucleic acids into cells to achieve transfection of the loaded cells. The terminology of electroporation, electrotransfection and electroloading have been interchangablly used in the literature with emphasis on general meaning of this technology, the transgene expression and the transference of molecules into cytoplasm, respectively. Hereinafter this method of transfecting cells is referred to as electroloading that is the method using electroporation with no transfecting reagent or biologically based packaging of the nucleic acid being loaded, such as a viral vector or viral-like particle, relying only on a transient electric field being applied to the cell to facilitate loading of the cell. Within electroporation, nucleofection is a special one involving a transfection reagent helping the transferred DNA in the cytoplasm to the nucleus. Nucleofection has been reported to transfect resting T cells and NK cells using plasmid DNA treated with a proprietary nucleofection agent (Maasho et al., 2004). It was also demonstrated that resting T cell nucleofection of chimeric receptor could lead to specific target cell killing (Finney, et al, 2004). Many reports showed that nucleofection or electroloading with DNA resulted in cell toxicity to resting hematopoietic cells including lymphocytes, dendritic cells and NK cells (Trompeter et al. 2003; Li et al. 2006; Li et al. 2001; Li et al. 1999; Landi et al., 2007; Van De Parre et al. 2005; Maasho et al. 2004; Abbott et al. 2006). Nucleofected resting NK cells or electrotransfected resting hematopoietic cells showed good transient viability and efficient transgene expression within a few hours after transfection and low viability after approximated 28 and 52 hours post-nucleofection and much decreased expression of a transgene at these times (Trompeter et al. 2003). Accordingly, this method of transient DNA transfection would not provide for a clinically useful preparation of transiently modified resting NK and T cells. Moreover, the transfection efficiency of fresh resting NK cells was about half that of growing NK cell lines.
Loading of cells with mRNA brings several advantages, and potentially could overcome problems associated with DNA transfection, especially in respect to resting cells and cells that will be infused into a patient. First, mRNA, especially when loaded by electroloading results in minimal cell toxicity relative to loading with plasmid DNA, and this is especially true for electroloading of resting cells such as resting NK and peripheral blood mononuclear cells (PBMC) cells. Also, since mRNA need not enter the cell nucleus to be expressed resting cells readily express loaded mRNA. Further, since mRNA need not be transported to the nucleus, or transcribed or processed it can begin to be translated essentially immediately following entry into the cell's cytoplasm. This allows for rapid expression of the gene coded by the mRNA. Moreover, mRNA does not replicate or modify the heritable genetic material of cells and mRNA preparations typically contain a single protein coding sequence, which codes for the protein one wishes to have expressed in the loaded cell. Various studies on mRNA electroloading have been reported (Landi et al., 2007; Van De Parre et al. 2005; Rabinovich et al. 2006; Zhao et al., 2006).
For a number of medical reasons autologous immunotherapy with resting unstimulated NK, T, PBL, and PBMC and allogeneic immunotherapy for resting unstimulated NK cells can be advantageous for treatment of cancer. In this context a method that allows removal of cells from the patient, their treatment outside the body, and their subsequent infusion in to the patient in minimal time, with minimal intervening procedure, and with minimal addition of foreign materials, particularly materials that contain replicating genetic information, or are antigenic, is desired for safety, and reasons of cost and efficiency. A method that allows modification of these cells without need of extensive cell culture, more specifically without the need for the cells to undergo cell division outside the body, comprises loading only of a nucleic acid that codes for only the therapeutic protein and which is not capable of replicating in the cells or modifying the genome of the cell that has been removed from the patient, and which will be returned to the patient, and which additionally does not involve the use of any other biologically or immunologically active components is desired.